The present invention relates to a magnetic head for a magnetic recording and reproducing apparatus and a manufacturing method of the magnetic head, and a magnetic recording and reproducing apparatus using this magnetic head.
Because a magnetic recording and reproducing apparatus has been small sized and has had a large capacity, the volume per one bit recorded on a magnetic recording medium has become rapidly small. In order to detect a magnetic signal generated from this small volume of one bit as a large reproducing output, a magnetoresistive (MR) head has been developed. This MR head is described in a technical report written by R. P. Hunt, xe2x80x9cA Magnetoresistive Readout Transducer,xe2x80x9d IEEE Trans. Mag., MAG-7, No. 1, 1971, pp. 150-154.
Further, a giant MR (GMR) head used a GMR effect, which can realize a largely higher output compared with the MR head, has been put to practical use. In this GMR effect, especially, the change of resistance corresponds to a cosine between the magnetizing directions of two adjacent magnetic layers. At an MR effect called a spin-valve effect, a large change of resistance is generated in a small operating magnetic field, therefore, the GMR head using this spin-valve effect has been largely used. This GMR head using the spin-valve effect is described in a technical report written by C. Tsang et al., xe2x80x9cDesign, Fabrication and Testing of Spin-Valve Read Heads for High Density Recording,xe2x80x9d IEEE Trans. Mag., Vol. 30, No. 6, 1994, pp. 3801-3806. In this technical report, one of two magnetic layers generating the spin-valve effect is a ferromagnetic pinned layer in which magnetization is fixed so that the direction of the magnetism substantially becomes the direction of the magnetic field of a magnetic recording medium that enters to a magnetic sensing part of the head, by an exchange magnetic field generated by layering an antiferromagnetic film on this one of the magnetic layers. And the other magnetic layer, which contacts with the ferromagnetic pinned layer via a conductive layer such as Cu, is a ferromagnetic free layer whose direction of the magnetism can be changed freely for the magnetic field of the magnetic recording medium. Hereinafter, this GMR head using the spin-valve effect is called a GMR head.
FIG. 1 is a diagram showing a structure of a conventional GMR head seen from an air-bearing surface (ABS) being a surface facing a magnetic recording medium. FIG. 2 is a sectional view of the conventional GMR head at the line AB in FIG. 1. As shown in FIGS. 1 and 2, at the conventional GMR head, a magnetism separating layer 3 made of an insulation material is formed between an upper shield 6 and a lower shield 2 layered on a ceramic 1 becoming a slider, and a spin-valve layered structure generating the GMR effect as a central region 4 is disposed in this magnetism separating layer 3. End regions 5, which supply current and a bias magnetic field to this central region 4, are formed at both ends of this central region 4. The part mentioned above is a GMR element for reproducing.
Further, the upper shield 6 is made to be a first magnetic core 6, and on the opposite side surface of the first magnetic core 6 existing the GMR element, a second magnetic core 11 is layered in parallel with the first magnetic core 6 via a recording gap 7. At the part between the first and second magnetic cores 6 and 11, a coil 9, which is covered with a non magnetizing insulator 8 and a non magnetizing insulator 10, is disposed. Recording is executed by using a magnetic flux generated from the recording gap 7 between the first and second magnetic cores 6 and 11 magnetized by a magnetic field generated by the coil 9. A structure, in which a reproducing head by the GMR element and a recording head by an inductive (ID) head are layered, is a practical GMR head.
The GMR head is actually used at a region in which the recording density is more than 3 G bits per square inche, that is, the region is a high density recording region. In case that the recording density is less than this, a conventional MR head using an anisotropic magnetoresistive (AMR) effect can be used sufficiently. That is, the GMR head usable practically is a head in which a high density recording and reproducing being more than 3 G bits per square inch can be realized. A magnetic recording and reproducing apparatus using the GMR head is a high density magnetic recording and reproducing apparatus that realizes the high density recording and reproducing being more than 3 G bits per square inch.
Not limited to the GRM head, an ID head having a recording function on a magnetic recording medium has been always required that its high density recording performance must be increased. Especially, in order to realize the high density recording, it is necessary that the magnetic recording medium has a high coercive force. Because a magnetic transition length recording on the magnetic recording medium is made to be short corresponding to the increase of the recording density, magnetization must be stable even as magnetization length per bit is made to be short. Consequently, in order that the ID head can record on a high coercive force magnetic recording medium being suitable for high density recording, the development to increase the recording magnetic field has been energetically promoted.
Conventionally, a plated film Nixe2x80x94Fe, in which Ni is about 80 weight % (hereinafter referred to as 80Nixe2x80x94Fe), has been used for a magnetic core of the ID head. This material has about 1 T (tesla) saturation magnetization (Bs), and can execute recording of 3 G bits per square inch. This is described in a technical report written by C. Tsang et al., xe2x80x9c3 Gb/in2 Recording Demonstration with Dual Element Heads and Thin Film Disks,xe2x80x9d IEEE Trans. Mag., Vol. 32, No. 1, 1996, pp. 7-12.
However, in order to perform recording of more than 5 G bits per square inches, a plated film Nixe2x80x94Fe, in which Ni is about 45 weight % (hereinafter referred to as 45Nixe2x80x94Fe) is required, instead of the 80Nixe2x80x94Fe. This is described in a technical report written by C. Tsang et al., xe2x80x9c5 Gb/in2 Recording Demonstration with Conventional AMR Dual Element Heads and Thin Film Disks,xe2x80x9d IEEE Trans. Mag., Vol. 33, No. 5, 1997, pp. 2866-2871. This material has saturation magnetization about 1.6 T at maximum. Further, recording of about 12 G bits per square inches can be executed by using this material is described in a technical report written by C. Tsang et al., xe2x80x9c12 Gb/in2 recording demonstration with SV read heads and conventional narrow pole-tip write heads,xe2x80x9d IEEE Trans. Mag., Vol. 35, No. 2, 1999, pp. 689-694.
In Japanese Patent Applications Laid-Open No. HEI 8-212512 and HEI 11-16120, a Nixe2x80x94Fe plated film having about 1.6 T saturation magnetization (Bs) is described. And in Japanese Patent Application Laid-Open No. HEI 10-162322, it is described that a Co type amorphous material represented by Coxe2x80x94Taxe2x80x94Zr sputtered film is used as a high saturation magnetization (Bs) material. About 1.5 T being the high saturation magnetization (Bs) is possible by using a Co type amorphous film. And in Japanese Patent Application Laid-Open No. HEI 7-262519, a high saturation magnetization (Bs) material such as ferric nitride is applied. About 1.9 T being the high saturation magnetization (Bs) is possible by using a Fexe2x80x94N type material.
In order to achieve simplification and low cost at manufacturing processes of a magnetic head, it is effective that a magnetic material forming a recording magnetic core is formed by a plating method. At the plating method, a photo resist frame, in which a pattern of a magnetic core is pressed, is formed beforehand, and a desired pattern can be obtained by making a plated film grow in this photo resist frame. This method is now a standard manufacturing method of a thin film magnetic head because of its simplicity and low cost.
In case that the magnetic core pattern is formed by a sputtering method, a photo resist mask is formed on a magnetic film formed beforehand so that the photo resist mask becomes a shape of a magnetic core, and the magnetic pattern is formed by applying etching used ion beam. However, in this method, first, it is necessary to install a high price ion beam etching apparatus, and second, it needs a long processing time to apply patterning to a magnetic film having several xcexcm thickness, and further, it is very difficult to form the tip part of the magnetic cores, which decides a recording width for the magnetic recording medium, to be a narrow width. Especially, as shown in FIG. 2, the upper surface of the second magnetic core 11 (upper magnetic core) has a large height difference because the coil 9 and the non magnetizing insulators 8 and 10 are disposed, therefore, it is very difficult to apply patterning to the second magnetic core 11 (upper magnetic core). In the Japanese Patent Applications Laid-Open No. HEI 7-262519, only the tip part of a magnetic core is formed before the large height difference is formed by a coil and insulation layers, and a Fexe2x80x94N sputtered film is formed on this part. However, the ion beam etching is used in this application, therefore this application can not realize a low cost manufacturing method. As mentioned above, applying the sputtering method to form the magnetic cores brings a cost increase caused by the complexity of the manufacturing processes.
As the recording density becomes high, a high saturation magnetization (Bs) film over 1.6 T obtained by 45Nixe2x80x94Fe is necessary. If this is realized by the plating method being low cost, this is very effective. Further a Coxe2x80x94Nixe2x80x94Fe type material can be considered as a material to realize the high saturation magnetization (Bs) over 1.6 T by applying the plating method.
In Japanese Patent Publication No. SHO 63-53277, an element map is shown in its FIG. 1. In the element map, a line of the magnetostriction xcexs=0 by a Coxe2x80x94Nixe2x80x94Fe plated film is shown. And in an element map shown in its FIG. 2, saturation magnetization (Bs) by the Coxe2x80x94Nixe2x80x94Fe plated film is shown. From these two element maps, it is disclosed that the saturation magnetization (Bs) of a 80Co-10Ni-10Fe plated film, in which magnetostriction xcexs substantially becomes zero, is about 1.6 T.
In Japanese Patent Applications Laid-Open No. HEI 6-346202, in order to realize both of the low magnetostriction (xcexs) and the large saturation magnetization (Bs), which were not realized by the Japanese Patent Publication No. SHO 63-53277 mentioned above, the crystallinity of the Coxe2x80x94Nixe2x80x94Fe plated film is adjusted. With the result of this adjustment, a Coxe2x80x94Nixe2x80x94Fe plated film being the magnetostriction xcexs less than 5xc3x9710xe2x88x926 and the Bs=about 1.7 T is obtained. And in Japanese Patent Applications Laid-Open No. HEI 7-3498, the crystallinity is also adjusted and the low coercive force is obtained and the large saturation magnetization Bs between about 1.3 T and 2.0 T is obtained. Further in Japanese Patent No. 2821456, a Coxe2x80x94Nixe2x80x94Fe plated film is formed in a plating bath not containing additives such as saccharin, and the sulfur concentration in the film is made to be less than 0.1 weight %, and a high purity film is realized. With this, against the Japanese Patent Publication No. 63-53277, mixed crystal composition of fcc and bcc is moved to a region where Fe composition is many, and the magnetostriction is decreased to a practical level by this composition, and a extremely large Bs being 1.9 T to 2.2 T with a good soft magnetic characteristic being that the coercive force is less than 2.5 Oe is realized.
As mentioned above, the Coxe2x80x94Fexe2x80x94Ni type plated film can realize a substantial soft magnetic characteristic as a magnetic core material of the magnetic head, by adjusting the crystallinity and by controlling the containing amount of the material mixed in the film. And as mentioned in the Japanese Patent No. 2821456, the magnetic core having an extremely large saturation magnetization Bs and a good soft magnetic characteristic can be realized.
However, the present invention found that the soft magnetic film having high purity and large saturation magnetization Bs shown in the Japanese Patent No. 2821456 shows a low resistivity value xcfx81 being less than about 20 xcexcxcexa9cm. Table 1 shows the saturation magnetization Bs and the resistivity xcfx81 of magnetic core materials that are applied to a magnetic core of a thin film magnetic head or will be applied in the future.
In the Table 1, the Coxe2x80x94Nixe2x80x94Fe film, whose soft magnetic characteristic is excellent and saturation magnetization (Bs) is large, is considered that the resistivity xcfx81 becomes low because of its high purity. As shown in the Table 1, at the plated film in which a low cost magnetic head can be realized, however, it is difficult to satisfy both a large saturation magnetization Bs about 2 T and a high resistivity xcfx81 at the same time. At the sputtered film, in case of a Fexe2x80x94N type, a large saturation magnetization Bs nearly 2 T can be realized with keeping a relatively high resistivity xcfx81. However, as mentioned above, it is technically difficult and brings a cost increase to apply a sputtered film to a magnetic core of a magnetic head, especially, to the upper magnetic core (the second magnetic core 11 in FIG. 1) to which a narrow width process is required.
On the other hand, in the case that a high purity Coxe2x80x94Nixe2x80x94Fe plated film is applied to a magnetic core for high density recording, the following problem occurs. That is, at the case of the high density recording, the data transfer rate is also required to be high, therefore, recording operation in a high frequency is needed. However, when a magnetic core material whose resistivity is low is used, the characteristic at the high frequency is deteriorated caused by its eddy current loss. At the high density recording region, in order to utilize the large saturation magnetization Bs characteristic of the high purity Coxe2x80x94Nixe2x80x94Fe plated film, it is necessary to improve the high frequency characteristic of the magnetic core of the magnetic head.
It is therefore an object of the present invention to provide a magnetic head and a manufacturing method of the magnetic head and a magnetic recording and reproducing apparatus using this head, in which the following problem is solved. A plated film realizing large saturation magnetization Bs about 2 T can not realize a high resistivity at the same time, therefore, when this plated film is applied to a magnetic head, the high frequency characteristic is deteriorated. This problem is solved at the present invention. Further, the present invention provides a magnetic head that is low cost and has large saturation magnetization Bs, and has an excellent high frequency characteristic suitable for a high density recording.
According to a first aspect of the present invention for achieving the object mentioned above, at a magnetic head, in which a coil insulated by insulation layers is disposed between a first magnetic core for recording and a second magnetic core for recording that is disposed to face the first magnetic core for recording via a recording gap, and which executes recording by that a magnetic flux of the first and second magnetic cores for recording excited by the coil is generated from the recording gap, at least one of the first and second magnetic cores for recording is composed of a first plated magnetic layer and a second plated magnetic layer in a state that the first plated magnetic layer is disposed at the near side of the recording gap, and saturation magnetization of the first plated magnetic layer is 1.7 T (tesla) or more, and when resistivity of the first plated magnetic layer is defined as xcfx811 and the thickness of the first plated magnetic layer is defined as xcfx811, and resistivity of the second plated magnetic layer is defined as xcfx812, and the thickness of the second plated magnetic layer is defined as xcfx812, xcfx811 less than xcfx812 and xcex41 less than xcex42.
According to a second aspect of the present invention, in the first aspect, the first plated magnetic layer is composed of mainly Co, Ni, and Fe.
According to a third aspect of the present invention, in the first aspect, the thickness of the first plated magnetic layer is 0.1 xcexcm or more, and is 1.0 xcexcm or less.
According to a fourth aspect of the present invention, in the first aspect, the second plated magnetic layer is composed of mainly Ni, and Fe.
According to a fifth aspect of the present invention, a composite type magnetic head provides a reproducing head in which a magnetoresistive effect element that reproduces by magnetoresistive effect is disposed and which is positioned in a insulation layer disposed between two magnetic shields, and a magnetic head in the first aspect, and one of the two magnetic shields is made to also work as the first magnetic core for recording.
According to a sixth aspect of the present invention, there is provided a manufacturing method of a magnetic head, and the first plated magnetic layer and the second magnetic layer are formed by an electrodeposition method.
According to a seventh aspect of the present invention, there is provided a magnetic recording and reproducing apparatus. The magnetic recording and reproducing apparatus provides a magnetic head in the first aspect.
According to an eighth aspect of the present invention, there is provided a magnetic recording and reproducing apparatus. The magnetic recording and reproducing apparatus provides a composite type magnetic head in the fifth aspect.